Population Trends of Ring-billed Gulls Breeding on the North American Great Lakes, 1976 to 2009

作者：Morris Ralph D^*; Weseloh D Vaughn; Wires Linda R; Pekarik Cynthia; Cuthbert Francesca J; Moore David J

来源：Waterbirds, 2011, 34(2): 202-212.

• breeding biology
• census counts
• Great Lakes
• Larus delawarensis
• population numbers
• Ring-billed Gulls

After near extirpation in the early 20th century, Ring-billed Gulls (Lures delawarensis) are currently (2009) the most abundant colonial waterbird nesting on the Great Lakes. Nest count data are reported from four decadal censuses (1976-2009) conducted by the Canadian Wildlife Service and the U.S. Fish and Wildlife Service. Numbers increased from 305,790 nests (1976-80) to a peak of 718,887 nests (1989-90), then decreased to 652,664 (1997-2000) and to 585,984 nests (2007-09). Changes varied spatially after the second census with greatest losses (-38.6%) at North Channel, Georgian Bay and northern Lake Huron colonies, and greatest gains (+324.2%) at Lake Michigan colonies. A total of 472 sites had nests in at least one census (Canada N = 319; U.S. N = 153). Eighteen (3.8%) colonies had >2,000 nests in all four censuses, and had 37.5-41.9% of all nests in each census. Site occupancy was fluid. A high proportion (56.8%, N = 268) of sites contained nests in only one of the four censuses, and few (N = 40,8.5%) had nests in all censuses. Thirty-nine sites had >2,000 nests gains/losses between census periods; 14 (35.9%) were on urban/industrial lands with artificial substrates. Human management and predator activities at some colonies contributed to declines in nest numbers at these locations. Movement of breeding birds among colonies and changes in local food supply may have influenced changes in nest numbers elsewhere. Reasons for the overall nest losses across the Great Lakes after the second census are unknown. Received 15 June 2010, accepted 30 August 2010.

• 出版日期2011-6